Limits of possible operation of the R-Tokamak due to ideal MHD instabilities
1
Citation
0
Reference
20
Related Paper
Cite
The need of durable and abundant energy sources for future ages stimulates the studies of thermonuclear energy sources, based on hot plasma confinement by magnetic fields. The most developed concept of hot plasma trap is the tokamak, where the plasma confinement is obtained by a combination of external magnetic fields with the magnetic field of the current flowing in the plasma torus. The stability of the tokamak plasma is the main subject of the present work. The hot plasma is approximated by the model of the ideal magnetohydrodynamics (ideal MHD) as a superconductive liquid. Being relatively simple, this model describes basic plasma stability properties and establishes necessary stability conditions. The analytical ideal MHD theory is well developed, but some assumptions, required for analytical treatment may not be valid for the plasmas of modern tokamaks and for future tokamak-based reactors. To circumvent this numerical codes have been created. These codes are free from such limitations, but they are not as convenient in use as analytical formulae. In the present work the validity of the analytical approach for the conditions of tokamaks like TCV and MAST is examined in comparison with numerical code predictions by studying the dependence of the ideal MHD stability on plasma toroidicity and shape parameters. The experimental study of the plasma dependence on triangularity, carried out on the TCV tokamak, is consistent with the results of the numerical calculations. A new formula, describing the ideal MHD stability dependence on plasma toroidicity and shape parameters is proposed for use in modern tokamaks and future reactors. This formula could be used instead of analytical expansions, which are not valid in such conditions. The ideal MHD stability of highly elongated TCV plasmas has been studied using numerical codes and the optimum plasma shape, which allows higher plasma performance, was found. Experimental data on the high elongation plasmas in TCV are consistent with the numerical predictions. Advanced tokamak plasma configurations, which provide better plasma properties, are amongst the main goals of the TCV tokamak research activity. The ideal MHD stability analysis of such plasmas, using numerical codes, can be useful for optimization of plasma parameters, and designing new experiments with improved plasma performance. Reversed shear plasmas with internal transport barrier were analyzed and the influence of the plasma pressure and current profiles on the ideal MHD stability of these plasmas was examined in detail. By fine tuning of the electron cyclotron heating and current drive system of TCV it was found that it might be possible to improve the plasma performance in reversed shear plasmas, by creating the optimal current and pressure profiles.
Plasma stability
Thermonuclear Fusion
Spherical tokamak
Safety factor
Cite
Citations (4)
Cite
Citations (0)
Tearing
Cite
Citations (4)
The experimental and theoretical researches on high-beta tokamaks are surveyed. The basic properties of ballooning modes and the recent progress in high-beta studies are discussed with emphasis on the beta scaling laws, the accessibility to the “second stability” high-beta region, the excitation of new instabilities, the degradation of the plasma confinement and the future plans for high-beta tokamaks.
BETA (programming language)
Ballooning
Cite
Citations (0)
Resistive touchscreen
Code (set theory)
Cite
Citations (32)
Cite
Citations (1)
The tokamak reactor becomes a more attractive fusion power source if it can operate in steady state, and at high fusion power density, with low recirculating power. This implies that a ‘‘steady-state advanced tokamak’’ must achieve both high beta and high confinement, consistent with a high fraction of the total plasma current being carried by the bootstrap effect. The most attractive mode of operation to fulfill these requirements involves a reversal of the global magnetic shear, dq/dr, in the plasma core. This allows self-consistency between the radial profile of the bootstrap current and that of the total current, while simultaneously reducing turbulent transport in the plasma core and increasing magnetohydrodynamic (MHD) stability. In this paper both theoretical and experimental work on the steady-state advanced tokamak are reviewed, and we point to new research areas that need to be pursued to make this concept a reality. Presently operating devices can make strong contributions in this research area, and future devices should be designed with the capability to access, investigate, and exploit this operating mode.
Bootstrap current
Plasma stability
Cite
Citations (20)
Cite
Citations (2)
Aspect ratio (aeronautics)
Bootstrap current
Cite
Citations (0)
Limitations on high-..beta.. tokamaks are imposed by a number of ideal and resistive MHD instabilities. The present paper reports results on three such studies: (1) Numerical analysis using the Princeton PEST code on ..beta.. optimization of tokamaks for low toroidal mode numbers n; (2) analytic and numerical results on ideal ballooning modes with high n; and (3) analytic and numerical results on resistive ballooning modes at high n.
Ballooning
BETA (programming language)
Resistive touchscreen
Cite
Citations (4)